1. Field of the Invention
This invention relates to a waveform synthesizing apparatus adapted to produce a desired synthesized waveform by adding partial waveforms together.
2. Description of the Prior Art
FIG. 1 is a block diagram of one example of a prior art electronic musical instrument of a type for generating a synthesized waveform by adding partial waveforms together. This system is disclosed in more detail in U.S. Pat. No. 3,854,365. In the system of FIG. 1, peak values of each-order harmonic wave, or of each partial waveform, are read out from a read-only memory (ROM) as a digital signal by corresponding sampling frequencies, and thus read-out data is subjected to frequency operation. An operation output obtained by the above frequency operation is multiplied by digital data of tone spectrum, time spectrum, envelope, loudness and the like in order, and the resultant output is converted into an analog signal which is obtained through a filter at an output end.
However, when peak values of each partial waveform are operated by the same operation frequencies as mentioned above, the peak values of respective partial waveforms are required to be individually memorized in a memory, so that the capacity of the memory becomes gigantic and also the number of operations is increased. Particularly, in the case of a polyphonic system, it is necessary to provide a memory at every sound and also to provide operation circuits for plural sounds in parallel. As a result, the construction becomes quite complicated.
Another prior art system is disclosed in U.S. Pat. No.